TMK for PS/2 keyboard

[equalunique]

I am wondering what's required to connect a TMK keyboard to a PS/2 port on a computer.

Will stock TMK support this, or is there more coding required? Is it dependent on the TMK keyboard? Has it been done? Is it hard to do?

I'd be interested in doing this with QMK too, but I haven't found anyone messing with PS/2 keyboard input using QMK. For TMK, there are some posts about converting from PS/2 to USB, but that's like the opposite of what I'm looking for.

[Thereminz]

have you tried of those simple usb to ps/2 converters, might work.

[Findecanor]

No, those simple green or purple adapters don't work: they are for devices that are capable of both protocols over the same wires. A real USB-to-PS/2 converter is a bit difficult to find.

From what I have seen in the source code, TMK supports only PS/2 input (keyboard adapter, or mouse/trackpoint), not output.
There is another firmware that speaks PS/2 but it is different internally: "ps2avr".

[rich1051414]

No, those simple green or purple adapters don't work: they are for devices that are capable of both protocols over the same wires. A real USB-to-PS/2 converter is a bit difficult to find.

From what I have seen in the source code, TMK supports only PS/2 input (keyboard adapter, or mouse/trackpoint), not output.
There is another firmware that speaks PS/2 but it is different internally: "ps2avr".

There is a possibility the passive USB to PS/2 adapter will work, but only on a modern computer with those hybrid PS/2 ports in the back, as they usually autodetect the protocol and can run a keyboard in ps/2 or USB mode, prefering ps/2 mode. The reason it is there is to enable n-key rollover when possible, but falling back to USB if not. Either way, this CANNOT work on a computer that has no support for USB in the first place.